A phased antenna array is a group of antennas in which the relative phases of the respective radio frequency (RF) signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. One prominent use of such antenna arrays is to enable beamforming and beamsteering. Beamforming is the coherent summing of directionality such that signals are additive rather than random. When transmitting, a beamformer controls the phase and relative gain of the RF signal at each antenna element, based upon various algorithms, in order to create a coherent pattern in the wavefront. Beamsteering, on the other hand, refers to the concept of changing the direction of the main lobe of a radiation pattern by switching antenna elements or by changing the relative phases of the RF signals driving the elements.
With multiple antenna elements and related circuitry, calibration is an issue since it is difficult to achieve the same output power across each antenna in the array for a given gain setting. If the phase of the RF signal provided to the antenna elements is not properly calibrated to account for such phase offsets, the directional or omnidirectional beam patterns emanating from the antenna may be distorted and/or misdirected.
Antenna arrays can be implemented using individual antenna elements on an integrated circuit (IC), on a printed wiring board (PWB), or as separate components. In the case of an IC antenna array with IC-based amplifiers and related circuitry, matching can be approached by very precise attention to design and fabrication. While this may produce the desired results, it significantly increases manufacturing costs. In the case of a PWB implementation, controlled impedance and equal trace lengths can contribute to making each circuit perform identically. However, this can be time consuming, costly to implement and difficult to simulate. Calibration is further complicated when performed for antenna arrays which are expected to be placed in service under varying operating conditions.
As such, what is needed is a system and method for calibrating antenna arrays in order to overcome one or more of the aforementioned drawbacks.